The Effects of Coral Bleaching on Marine Life

Background

• Colonial invertebrates related to jellyfish form coral reefs. They secrete calcium to provide protection and support, and over time the secretions build up into huge reefs. The corals provide the backbone of the habitat and also food for higher animals. Coral animals live symbiotically, which means they have a mutually dependent relationship with microorganisms. These single-celled creatures provide the color of reefs. When the coral's symbiotic creatures are gone, you see only the white skeletons left behind, hence the term "coral bleaching." The coral animals usually die shortly afterward. When the corals die, essentially the reef dies also. Coral bleaching is caused by various environmental factors, including temperature changes, increasing acidity and pollution.

Loss of Food Supply

• A number of reef fish feed primarily on coral animals. After coral bleaching, the coral animals are replaced by algae, which may be a short-term replacement food. However, over a longer period, the basis of the food chain is lost. As a result, the fish and invertebrates that feed on coral and the animals that feed on them in turn also die out.

Loss of Habitat

• Coral reefs provide an intricate network of shelters, attachment sites for sessile organisms such as anemones, and breeding areas that are unusual in the ocean. They are vulnerable to erosion from the movement of water and from organisms that feed on coral skeletons. The coral skeletons do provide habitat after the corals, but without corals continuously building and rebuilding the reef, the reef gradually wears away. Extreme weather events such as hurricanes can quickly flatten areas of reef.

Biodiversity

• Coral reefs support great biodiversity, including at least a quarter of all known fish species. When the reef dies, the animals that depend upon it soon follow. Many of these creatures can live in no other habitat and many other marine animals are dependent upon reefs for food. It impacts humanity as well. Among the animals that directly or indirectly depend on coral reefs are commercially important species such as lobsters and fish.